Yalta? That was 80 years ago. And the party which you're referring to has not existed for over 30 years. And we did actually allow the soviets to keep the agreed-to territory... while they actually existed.

Post USSR, there was some *discussion* about limiting the scope of NATO, but certainly no agreements or treaties.

As the Russian sphere dwindles, they tend to want to coerce their former subject states into remaining subjugated. Not surprisingly, that drives them into the western sphere. And Finland and Sweden would have been perfectly happy staying neutral... if vlad hadn't rolled the red army in the general direction of the Fulda Gap.